1. Field of the Invention
The present invention generally relates to skeletal muscle stimulation, and more particularly, it relates to improved steroid eluting intramuscular lead systems.
2. Description of the Prior Art
The use of skeletal muscle tissue to power chronically implantable cardiac assist systems is expected to become increasingly available and common. U.S. Pat. No. 4,411,268, issued to Cox, and U.S. Pat. No. 4,813,952, issued to A. Khalafalla, both assigned to Medtronic, Inc., and incorporated herein by reference, describe such a cardiac assist system.
By using the patient's own muscle tissue to overcome the problems associated with storage and transmission of
By using the patient's own muscle tissue to overcome the problems associated with storage and transmission of energy from artificial sources, results in a compact and energy efficient system which requires no percutaneous energy transmission. Such cardiac assist system is however not without its limitations. One problem presented by the use of skeletal muscle power is the application of stimulation signals to cause muscle contraction.
The earliest skeletal muscle powered cardiac assist systems used screw-in type leads for skeletal muscle stimulation. A major improvement to these leads is found in the use of steroid eluting pacing leads. U.S. Pat. No. 4,711,251 issued to Stokes, and assigned to Medtronic, Inc. teaches the use of an endocardial pacing lead having steroid drug embedded in the distal tip. This embedded steroid drug treats the heart tissue immediately in contact with the pacing electrode. U.S. Pat. Nos. 4,506,680; 4,577,642; and 4,606,118 teach similar endocardial leads, all of which treat the electrode contact area with a steroid. United States Statutory Invention Registration No. H356 discloses an endocardial pacing lead suitable for epicardial insertion which elutes a steroid drug from the electrode.
All of these pacing leads are directed to stimulating the heart muscle. The skeletal muscle used to power the cardiac assist system is likely to be configured in a wide variety of shapes, any specific one of which cannot be known until the surgical procedure is actually performed. For that reason a flexible, specifically designed lead is far more appropriate for stimulating muscle than one especially directed to cardiac pacing applications.